(a) Field of the Invention
The present invention relates to a liquid crystal display adaptive to a viewing angle. More specifically, the present invention relates to a liquid crystal display capable of adaptively selecting a gamma curve based on the viewing angle.
(b) Description of the Related Art
In general, a liquid crystal display (LCD) has a transparent electrode installed on the inner sides of two substrates in various display modes, e.g., in a twist nematic (TN) display mode in which liquid crystal molecules having a positive (+) dielectric isotropy are arranged in parallel with the substrates and twisted with an angle difference of almost 90 degrees between the substrates, and a super twist nematic (STN) display mode in which the liquid crystal molecules are arranged in a similar way to a TN display mode but twisted with an angle difference of 180 to 240 degrees between the substrates.
FIG. 1 is a diagram illustrating a transmissivity depending on an applied voltage in a normally white mode-type TN liquid crystal.
Referring to FIG. 1, the curves graph the transmissivity based on a voltage applied from the front of the LCD (i.e., at an angle of 0 degrees) and at a predetermined angle from the LCD, for example, at a viewing angle of −20 degrees, respectively.
Thin film transistor (TFT) LCD products with such a characteristic of the TN LCD mode have a problem in displaying grays based on the viewing angle. Namely, those grays as normally viewed from the front of the LCD panel are difficult to see at a viewing angle other than zero degrees.
As such, the range of the viewing angle is more significant in a color display relative to a black-and-white one. The movement of the observer varies the display contrast and color, since the viewing angle is not uniform in all directions unless the liquid crystal molecules displaying optical double refraction are in a completely parallel or vertical array.
Besides, the LCD module is designed to apply a constant voltage to the liquid crystals in order to optimize the gray representation from the front side of the LCD, which gives rise to a problem that the gray turns black even with a lowest voltage.
The LCD panel cannot maintain an accurate gray level based on the viewing angle, for example, in a notebook computer in which the user must open the LCD panel wide, in which case the LCD panel has a limitation in the wide-open area during use due to the viewing angle.